Re: [trill] seeking help to understand a line from TRILL-ESADI draft

[Donald Eastlake <[e-mail]>]

Currently there are no Hellos in ESADI. Participation is determined
from the core IS-IS link state database.

Thanks,
Donald
=============================
 Donald E. Eastlake 3rd   [phone] (cell)
 155 Beaver Street, Milford, MA 01757 USA
 [e-mail]


On Wed, Jul 18, 2012 at 3:12 PM, Radia Perlman <[e-mail]> wrote:
> Actually, perhaps ESADI shouldn't bother with CSNPs at all.  If each
> RB participating in the ESADI instance included the sequence number of
> its own LSP in its Hello for that ESADI instance, wouldn't that work?
> We need to have each RB (in the ESADI instance) send Hellos
> periodically anyway.
>
> Radia
>
> On Wed, Jul 18, 2012 at 11:15 AM, Thomas Narten <[e-mail]> wrote:
>> Seems to me that the MAY sentence all by itself is not helpful.
>>
>> If sending occasionaly ESADI-CSNPs increases robustness, IMO, the spec
>> should say that and explain which scenarios its useful in. And then,
>> MAY doens't seem right either. SHOULD would seem to make more sense...
>>
>> The RFC 2119 defintion of MAY says:
>>
>> 5. MAY   This word, or the adjective "OPTIONAL", mean that an item is
>>    truly optional.  One vendor may choose to include the item because a
>>    particular marketplace requires it or because the vendor feels that
>>    it enhances the product while another vendor may omit the same item.
>>    An implementation which does not include a particular option MUST be
>>    prepared to interoperate with another implementation which does
>>    include the option, though perhaps with reduced functionality. In the
>>    same vein an implementation which does include a particular option
>>    MUST be prepared to interoperate with another implementation which
>>    does not include the option (except, of course, for the feature the
>>    option provides.)
>>
>> which doesn't seem to match the explanation for why the MAY sentence
>> is in the document.
>>
>> Thomas
>>
>> Donald Eastlake <[e-mail]> writes:
>>
>>
>>> Hi Swet,
>>
>>> On Tue, Jul 17, 2012 at 5:59 AM, Swet kumar <[e-mail]> wrote:
>>> > Hi Authors,
>>> >
>>> >
>>> > I am not able to understand the meaning of the following line in this draft:
>>> > http://tools.ietf.org/pdf/draft-ietf-trill-esadi-00.pdf
>>
>>> Thanks for reviewing this document. It was just recently posted as a
>>> WG document and I think it does need some more work.
>>
>>> > “For robustness, if an ESADI instance has two or more ESADI neighbors
>>> >
>>> >    and is not DRB and it receives no ESADI-CSNP PDUs for at least the
>>> >
>>> >    CSNP Time (see Section 6.1) of the DRB, it MAY transmit an ESADI-
>>> >
>>> >    CSNP.”
>>
>>> Do you really no understand what the sentence says? Or is it that you
>>> don't understand what the reason is for this behavior?
>>
>>> The idea is that if the DRB on an ESADI virtual link is being flakey
>>> or the virtual link is broken then, to maintain LSP synchronization,
>>> it would be good for some other TRILL switch on that ESADI virtual
>>> link to occasionally send a CSNP. The multi-hop ESADI pseudo-link is
>>> inherently somewhat less reliable that a link between adjacent TRILL
>>> switches. (You might think this could result in a flurry of CSNPs but
>>> note that, due to the jitter in the IS-IS reliable flooding mechanism,
>>> if there were several non-DRB TRILL switches on the link, as soon as
>>> one sends a CSNP it will inhibit the others for a while.)
>>
>>> Anyway, although it doesn't make much difference. It should probably
>>> say "one" instead of "two" in the text and it should not just be that
>>> it has not received a CSNP but that it has not received or sent a
>>> CSNP. So, I think the wording should be changes to:
>>
>>>    "For robustness, if an ESADI instance has one or more ESADI neighbors
>>>    and is not DRB and it does not receive or send an ESADI-CSNP PDU
>>>    for at least the CSNP Time (see Section 6.1) of the DRB, it MAY
>>>    transmit an ESADI-CSNP."
>>
>>> Thanks,
>>> Donald
>>> =============================
>>>  Donald E. Eastlake 3rd   [phone] (cell)
>>>  155 Beaver Street, Milford, MA 01757 USA
>>>  [e-mail]
>>
>>> > This line is a part of section 4.1 (Sending of ESADI PDUs) on page number
>>> > 12.
>>> >
>>> > Please explain me what this line tries to convey.
>>> >
>>> >
>>> > Regards,
>>> >
>>> > Swet
>>> _______________________________________________
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>>> https://www.ietf.org/mailman/listinfo/trill
>>
>>
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